Chapter 13

Viruses, Viroids, and Prions

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A commensal bacterium

May be an opportunistic pathogen

Which of the following statements is trueA. Symbiosis refers to different organisms living together.B. Members of a symbiotic relationship cannot live without each otherC. A parasite is not in symbiosis with its host.D. Symbiosis refers to different organisms living together and benefiting from each other.E. At least one member must benefit in a symbiotic relationship.

A. Symbiosis refers to different organisms living together.

A nosocomial infection is

Always present but is inapparent at the time of hospitalization.

The major significance of Koch's work was that

Microorganisms cause disease

Koch's postulates don't apply to all diseases because

Not all diseases are caused by microorganisms

Which of the following diseases is NOT spread by droplet infection?A. BotulismB. TuberculosisC. MeaslesD. Common coldE. Diphtheria

Botulism

Mechanical transmission differs from biological transmission in that mechanical transmission

Doesn't involve specific diseases

Which of the following definitions is incorrect?A. Endemic - Disease constantly present in populationB. Epidemic - fraction of the population having a disease at a specific timeC. Pandemic - affects a large number of people in the world in a short time.D. Sporadic - affects population occasionally.E. Incidence - number of new cases of a disease

Epidemic - fraction of the population having a disease at a specific time

Which infection can cause septicemia?

Focal infection

Which type of infection can be caused by septicemia?

Systemic infection

Koch observed Bacillis anthracis multiplying in the blood of cattle. What is this condition called?

Which statement about nosocomial infections is falseA. They occur in compromised patientsB. They are casued by opportunistsC. They are caused by drug-resistant bacteriaD. They are caused by normal microbiotaE. The patient was infected before hospitalization.

The patient was infected before hospitalization

Regular washing with antibacterial agents is the removal of normal microbiota which can result in

Increased suseptibility to disease

Which is NOT a resevior of infection?A. Sick personB. Healthy personC. Sick animalD. HospitalE. All can be reseviors of infection

All can be reseviors of infection

Which is NOT a communicable disease?A. MalariaB. AIDSC. TuberculosisD. TetanusE. Typhoid fever

Tetanus

Which of the following is a fomite?A. WaterB. Droplets from a sneezeC. PusD. InsectsE. Hypodermic needle

Hypodermic needle

Which statement is false about biological tramsmission?A. The pathogen reproduces in the vectorB. The pathogen may enter the host in the vector's fecesC. Houseflies are an important vectorD. The pathogen may be injected by the bite of the vectorE. The pathogen may require the vector as a host

Houseflies are an important vector

Which of the following definitions is incorrect?A. Acute - a short-lasting primary infectionB. Inapparent - infection characteristic of a carrier stateC. Chronic - a disease that develops slowly and lasts for monthsD. Primary infection - an initial illnessE. Secondary infection - a long-lasting illness

Secondary infection - a long-lasting illness

Symptoms of disease differ from signs of disease in that symptoms

Are changes felt by the patient

The science that deals with when diseases occur and how they are transmitted is called

Epidemiology

Graph of influenza during a typical year indicates the endemic level

B

Emergence of infectious diseases can be due to the following exceptA. Antibiotic resistanceB. Climatic changesC. Digging up soilD. Microbes trying to cause diseaseE. Travel

Which of the following can contribute to postoperative infections?A. Using syringes more that onceB. Normal microbiota on the operating room staffC. Errors in aseptic techniqueD. Antibiotic resistanceE. All of the above

All of the above

What is the endemic level of rotavirus infections? (according to figure 14.2)

Approximately 20%

A cold transmitted by a facial tissue is an example of

Vehicle transmission

Influenza transmitted by an unprotected sneeze is an example of

Droplet transmission

A sexually transmitted disease is an example of

Direct contact

Gastroenteritis acquired from roast beef is an example of

Direct contact

A needlestick is an example of

Fomite

Legionellosis transmitted by a grocery story mist machine is an example of

Vehicle transmission

Plague transmitted by a flea is an example of

Vector

The most likely mode of transmission of pneumonic plague between humans is

Droplet transmission

Situation 14.1239 cases of pneumonia in a town of 300 w/i a 6 month period along with a confirmed case of positive result for antibodies against Coxiella burnetti in sheep which 20 out of 2000 tested, 15 were positive. Weather with wind from the northwest where the sheep were kept and rainfall was factored inThis is an example of

Haemophilus bacteria require heme protein produced by Staphylococcus bacteria. This is an example of

Synergism

Which of the following is NOT a zoonosis?A. Cat-scratch diseaseB. Hantavirus pulmonary syndromeC. RabiesD. TapewormE. All are zoonosis

All are zoonosis

Pseudomonas bacteria colonized the bile duct of a patient following his liver transplant surgery. This is an example of

Nosocomial infection

Figure 14.3 shows incidence of polio in the United States. The period between 1945-1955 indicates

An epidemic level

Which of the following statements is false?A. Antimicrobial therapy for hemodialysis-associated infections increases antibiotic resistance.B. S. aureus is differentiated from other mannitol+ cocci by the coagulase testC. The M in MRSA stands for mannitolD. USA100 accounts for most hospital-acquired MRSA.E. USA300 accounts for most community-acquired MRSA

The M in MRSA stands for mannitol

Endemic

A disease that is constantly present in a population

Epidemic

Many people in a given area acquire a certain disease in a relatively short period

Pandemic

A disease that affects a large number of people in the world in a short time

Sporadic

A disease that affects a population occasionally

Incidence

The number of new cases of a disease

Which of the following statements is(are) wholly characteristic(s) of viruses?A. Viruses contain either DNA or RNA; and they undergo binary fusion.B. Viruses' requirements for the availability of cellular factors, within the potentialhost cell, required for viral multiplication determine its morphology.C. Viruses possess enzymes for protein synthesis and ATP generation.D. Requirements for a virus to specifically attach to the host cell determine itsparticular host range.

D. Requirements for a virus to specifically attach to the host cell determine itsparticular host range.

Hemagglutination is associated with which structural component of certain viruses?

Spikes

If a patient exhibits symptoms associated with the common cold and upper respiratory tract infections, whichviral genus is the likely culprit?

Coronavirus

Which of the following is true regarding cultivation and isolation of animal viruses?A. Primary cell lines are transformed cells that can be maintained through anindefinite number of generations.B. Diploid cell lines are widely used for culturing viruses that require a humanhost.C. Mice provide a reliable model for studying viral replication and for developingvaccines.D. The preferred and widely used method of viral isolation and growth is viagrowth in an embryonated egg.

B. Diploid cell lines are widely used for culturing viruses that require a humanhost.

Regarding the biosynthesis of DNA viruses, components of which virus family are synthesized in the host cellcytoplasm?

Poxviridae

Which of the following virus families transcribes viral DNA in the host nucleus, with host enzymes, and uses reverse transcriptase to make viral DNA from mRNA?A. ReoviridaeB. PapovaviridaeC. ParvoviridaeD. Hepadnaviridae

D. Hepadnaviridae

What is the correct sequence of events during the replication of a DNA-containing animal virus?1 - Virions mature.2 - Capsid proteins are synthesized.3 - Virions are released.4 - Early viral proteins are encoded as viral DNA is transcribed.5 - Virion enters host cell and its DNA is uncoated.6 - Virion attaches to host cell.7 - Viral DNA is replicated, and some viral proteins are made.

6-5-4-7-2-1-3

Which clinical feature or special feature applies to the papovaviridae family of viruses?A. Its viruses induce tumors as host cells may proliferate.B. Viral DNA is transcribed, by cellular enzymes, in the nucleus of the host cell.C. Its papillomavirus genus produces warts in humans.D. Its viruses induce tumors as host cells may proliferate. Its papillomavirus genus produces warts in human. Viral DNA is transcribed, by cellular enzymes, in the nucleus of the host cell.

D. Its viruses induce tumors as host cells may proliferate. Its papillomavirus genus produces warts in human. Viral DNA is transcribed, by cellular enzymes, in the nucleus of the host cell.

Which of the following statements regarding lysogeny is true?a)During lysogeny, most phage genes are repressed by repressor proteins that areproducts of the host DNA.b)Occasionally, rare spontaneous events, such as ultraviolet light, can lead to rapidincorporation of phage DNA into the host cell DNA.c)During lysogeny, phage genes are turned on, in order to synthesize new virions.d)During lysogeny, most phage genes are repressed by two repressor proteins that arephage gene products.

b)During lysogeny, most phage genes are repressed by two repressor proteins that are phage gene products.

Regarding the multiplication pathways of RNA-containing viruses, which of the following are double-stranded RNA viruses that must use sense strand mRNA to code for proteins?

Which statement is incorrect regarding the biosynthesis of DNA and RNA viruses? a)Togaviridae use viral RNA as a template for synthesizing RNA polymerase, which copies sense strand RNA to make mRNA in the cytoplasm.b)Viral DNA is made from mRNA, via reverse transcriptase, in hepadnaviridae.c)Reoviruses make mRNA by copying antisense strand RNA in the cytoplasm.d)Parvoviridae use cellular enzymes to transcribe viral DNA in the nucleus.

a)Togaviridae use viral RNA as a template for synthesizing RNA polymerase, which copies sense strand RNA to make mRNA in the cytoplasm.

Which of the following is a characteristic of the infectious diseases caused by prions?

Which of the following conditions in humans is linked to bovine spongiform encephalopathy?

Variant Creutzfeldt-Jakob disease

What part of the nervous system is most affected by fatal familial insomnia?

Thalamus

Where does the name "scrapie" come from?

The prion disorder causes infected sheep to scrape against objects until their skin is raw.

From which phrase is the term "prions" derived?

Proteinaceous infectious particles

In what year did Stanley Prusiner discover prions?

1982

Which disease did Stanley Prusiner first identify as being caused by prions?

Scrapie

How are prions different from other infectious agents?

They lack nucleic acid

Contributes to antigenic shift in influenza viruses?

Segmented genome

Most RNA viruses carry which of the following enzymes?

RNA-dependent RNA polymerase

Most likely a product of an early gene?

DNA polymerase

Nontoxic strains of Vibrio cholerae can become toxic when they are in the human intestine with toxic strains of bacteria. This suggests that the toxin genes are acquired by

Transduction

Some viruses, such as human herpesvirus 1, exist in a cell without causing symptoms; these are called

Latent viruses

Which of the following is not characteristic of viroids? a)Its internally paired nucleotides' three-dimensional structure helps protect it from attack by cellular enzymes.b)There are similarities between the base sequences of viroids and exons, resulting in the hypothesis that viroids evolved from exons.c)Viroids are short pieces of naked RNA.d)Viroids are typically 300 to 400 nucleotides long.

b)There are similarities between the base sequences of viroids and exons, resulting in the hypothesis that viroids evolved from exons.

How do viruses differ from bacteria?

Viruses are filterableViruses are not composed of cells

Which of the following statements provides the most significant support for the idea that viruses are nonliving chemicals? a)They are not composed of cells.b)They are filterable.c)They cause diseases similar to those caused by chemicals.d)They cannot reproduce themselves outside a host.e)They are chemically simple.

d)They cannot reproduce themselves outside a host.

Which of the following statements about spikes is false? a)They are used for absorption.b)They are used for penetration.c)They may cause hemagglutination.d)They are found only on enveloped viruses.

b)They are used for penetration

What is used as criteria to classify viruses?

MorphologyNucleic acidSizeNumber of capsomeres

Which of the following is NOT a method of culturing viruses?a)In laboratory animalsb)In cell culturec)In embryonated eggsd)In culture mediae)None of the above

d)In culture media

The definition of lysogeny is

Phage DNA is incorporated into host cell DNA.

A viroid is

A nonenveloped, infectious piece of RNA

A clear area against a confluent "lawn" of bacteria is called a

Plaque

The most common route of accidental AIDS transmission to health care workers is

needlestick

An example of a latent viral infection is

cold sores

Which of the following contributes to the difficulty in establishing the etiology of cancer? a)Most viral particles can infect cells without inducing cancer.b)Cancer may not develop until long after infection.c)Cancers do not seem to be contagious.d)Viruses are difficult to observe.e)All of the above.

e) all of the above

An envelope is acquired during which step?

Release

An infectious protein is a

prion

What is the first step in biosynthesis of a virus with a - strand of RNA?

Synthesis of double-stranded RNA from an RNA template

Lysogeny can result in all of the following EXCEPTa)Immunity to reinfection by any phage.b)Acquisition of new characteristics by the host cell.c)Immunity to reinfection by the same phage.d)Transduction of specific genes.e)None of the above.

a)Immunity to reinfection by any phage.

Which of the following statements is false? a)A prophage is phage DNA inserted into a bacterial chromosome.b)A prophage can pop out of the chromosome.c)The prophage makes the host cell immune to infection by other phages.d)A prophage may result in new properties of the host cell.e)Prophage genes are represented by a repressor protein coded for by the prophage.

c)The prophage makes the host cell immune to infection by other phages.

A persistent infection is an infection in which

the disease process occurs gradually over a long period

What is necessary for replication of a prion?

pSc

Continuous cell lines differ from primary cell lines in that

Continuous cell lines can be maintained through an indefinite number of generations.

The most conclusive evidence that viruses cause cancers is provided by

cancer following injection of cell-free filtrates

Bacteriophages derive all of the following from the host cell EXCEPTa)tRNA.b)Lysozyme.c)Amino acids.d)Nucleotides.e)A.T.P.

b)Lysozyme

Generally, in a DNA-containing virus infection, the host animal cell supplies all of the following EXCEPTa)RNA polymerase.b)DNA polymerase.c)Nucleotides.d)tRNA.e)All of the above are supplied by the host animal cell.

b)DNA polymerase

Put the following in the correct order for DNA-virus replication:1-Maturation; 2-DNA synthesis; 3-Transcription; 4-Translation.

2, 3, 4, 1

A viral species is a group of viruses that

Have the same genetic information and ecological niche.

Viruses that have reverse transcriptase are in the

Hepadnaviridae and Retroviridae

Which of the following statements about viruses is false? a)Viruses contain DNA or RNA but never both.b)Viruses use their own catabolic enzymes.c)Viruses use the anabolic machinery of the cell.d)Viruses contain a protein coat.e)Viruses have genes.